This invention relates to magnetic recording. In one aspect, this invention relates to an acicular, gamma ferric oxide which is doped with cobalt and is suitable for use in preparing magnetic recording materials, particularly high performance magnetic tapes exhibiting reduced print-through. In another aspect, this invention relates to a process for obtaining such an oxide and magnetic recording elements containing these oxides.
In the field of signal recording, it is obviously desirable to be able to prepare high performance magnetic recording elements, for example, magnetic tapes. It is also known that the capabilities of magnetic recording elements such as tapes, discs, drums, striped motion picture films and the like which are used for recording and reproduction of sounds, images and other signals are closely related to the properties of the magnetizable materials employed in these elements.
One of the more commonly used magnetizable particles for magnetic recording elements is acicular gamma ferric oxide having a particle length which is less than about 1.5 microns. Such acicular gamma ferric oxide can be obtained from ferric oxide hydrate which is then dehydrated to form alpha ferric oxide which is then reduced to form ferrous ferric oxide which in turn is oxidized to gamma ferric oxide.